1. Field of the Invention
The present invention relates to a screw driving tool having a housing with a neck section, an axially displaceable drive spindle located in the housing, a bit holder having a shank for releasably connecting the bit holder with the drive spindle, an axially adjustable depth stop surrounding the bit holder and a portion of the drive spindle and connectable with the housing, and a sleeve-shaped dust-repelling member arranged between the depth stop and the bit holder.
2. Description of the Prior Art
All of bit holders, which are presently available on the market, have a very slim shape. In order to prevent penetration of dust in the bit holder/drive spindle connection region and into the interior of the driving tool, U.S. Pat. No. 5,568,849 discloses use of a dust-repelling member which is arranged between the depth stop and the bit holder and extends from the bit holder/drive spindle connection region in the screw-in direction. The depth stop has a plurality of side opening formed in its circumference in the region of the dust-repelling member. Through these side openings, dust, which penetrates into the depth stop, is removed. The dust-repelling member, which is connected releasably with the depth stop, because of the rotation of the bit holder relative to the dust-repelling member, is subjected to extensive wear and, therefore, need be often replaced in order to insure that no dust penetrates into the bit holder/drive spindle connection region. For replacing the dust-repelling member, a special pull-out tool is required. Such a tool is not always available at a construction site.
Accordingly, an object of the present invention is to provide a screw driving tool with a dust-repelling member in which the dust-repelling member is not subjected to any wear.
Another object of the present invention is to provide a screw driving tool with a dust-repelling member which can be simply and rapidly replace, without the use of any special pull-out tool.
A further object of the present invention is to provide a screw driving tool with a dust-repelling member which reliably prevents any penetration of the dust inside the tool.
These and other objects of the present invention, which will become apparent hereinafter, are achieved, according to the present invention, by releasably connecting the dust-repelling member with the bit holder.
The advantage of connection of the dust-repelling member with the bit holder consists in that it is removed from the driving tool together with the bit holder that is securable to the drive spindle with a spring-biased locking member. The bit holder, together with the dust-repelling member, can be removed by applying a force to the locking member for displacing it in its release position. No special tool is need for disconnecting the dust-repelling member and the bit holder. It is sufficient to put the dust-repelling member against and edge of the constructional component and to pull the bit holder out of it. A further advantage of the present invention consists in that the entire outer profile of the dust-repelling member can be visually inspected for search of any conspicuous traces of wear.
In order to keep the radial extent of the bit holder together with the dust-repelling member small, the dust-repelling member preferably is releasably connected with the shank of the bit holder.
The dust-repelling member according to the present invention can be formed, e.g., of two cylindrical sections of which one, the first section, directly adjoins the receiving region of the bit holder and has the same diameter as the receiving region. The second section, which adjoins the first section has a larger diameter and an outer profile which is separated from the inner wall of the depth stop by an annular gap. This prevents any friction between the dust repelling member and the inner wall of the depth stop, and practically, the dust repelling member is not subjected to any wear.
In order to prevent penetration of dust through the annular gap between the dust-repelling member and the depth stop into the bit holder/drive spindle connection region, a circumferential profile means is provided on the outer surface of the dust-repelling member. A certain amount of dust can accumulate on this profile and which can be removed when the bit holder, together with the dust-repelling member, is removed from the screw driving tool.
Advantageously, the circumferential profile is formed as a left-hand trapezoidal thread. With a right-handed rotation of the drive spindle, the left-hand trapezoidal thread forms, together with the annular gap, a delivery channel through which the dust in the gap is transported in the screw-in direction and is removed through the side openings formed in the depth stop.
At the end of the second section of the dust-repelling member facing in a direction opposite the screw-in direction, there is provided a flange-shaped widening that projects radially beyond the circumferential profile provided on the outer surface of the dust-repelling member and beyond the inner wall of the depth stop. This flange-shaped widening has two functions. It serves for sealing a bearing location in the neck section of the housing and for sealing a section of the drive spindle which projects into a receiving opening of the dust-repelling member. The other function of the flange-shaped widening consists in that it serves as a throw-away disc that throws the dust, which settles on the flange-shape widening during the stoppage of the driving tool or as a result of shocks, radially outwardly, e.g., toward the depth stop, upon start of the driving tool. The accumulated dust reaches the left-hand thread on the outer surface of the dust-repelling member and is transported by the threads in the screw-in direction to the side openings in the depth stop.
For reducing weight, the dust-repelling member advantageously is formed of a plastic material.
An additional protection of the bit holder/drive spindle connection region is advantageously achieved with a sleeve-shaped connection member which is used for connecting the depth stop with the housing. The connection member completely surrounds, in the axial direction, the neck section of the housing and partially surrounds the depth stop. The connection member is axially fixed with respect to the neck section with a ball-shaped locking member located in a side bore of the connection member. The locking member is pressed into a circumferential indentation formed in the neck section of the housing with an O-ring that serves as tensioning means. The O-ring is located in a circumferential groove formed in the sleeve-shaped connection member.
A rapid and simple axial adjustment of the depth stop with respect to the housing is effected with thread connection means which connects the depth stop with the connection member. To this end, the depth stop is provided with an outer thread which cooperates with a corresponding inner thread of the connection member.
In order to reliably remove the dust, which penetrated into the space between the outer surface of the dust-repelling member and the depth stop, the connection member is provided with a through-bore, which extend transverse to the screw-in direction and into which a side opening, which is formed in the depth stop, opens.
The novel features of the present invention, which are considered as characteristic for the invention, are set forth in the appended claims. The invention itself, however, both as to is construction and its mode of operation, together with additional advantages and objects thereof, will be best understood from the following detailed description of preferred embodiments, when read with reference to the accompanying drawings.